The present invention relates generally to systems which monitor and record motion events, and it relates to cameras and systems for time-sequential imaging and display, with application in numerous fields. Most particularly, the invention provides a station imaging camera and system useful for measuring timed sporting events and imaging movement along defined tracks at stations. The invention also relates to systems and methods for generating a scene by compiling successively-scanned line objects, as described for example in applicant""s commonly-owned U.S. Pat. Nos. 5,552,824 and 5,657,077.
Prior art systems employing standard photographic techniques to monitor the finish line of a race are known. In such a system, typically one or more cameras equipped for high resolution imaging view the finish line and capture sequential pictures at a high rate for later inspection by a judge or other interpreter. However, this process is cumbersome, wasteful, and time-consuming, in that it requires, for example, an apparatus of photographic film and paper, processing chemicals, and image enlargers or projection optics to be employed with their respective methods of operation, development and finishing. Consequently, most races rely on human judges and revert to xe2x80x9cphoto-finishxe2x80x9d technology only in extremely close or important events. The Specialty Instrument Corporation provides a number of electronic and photo-finish systems of this type marketed under the trademark Accutrack. U.S. Pat. No. 3,829,869 exemplifies one such Accutrack system.
Because of the problems with the xe2x80x9cphoto-finishxe2x80x9d technology, numerous other systems for monitoring racing events have been developed. However, these other methods and systems for timing sporting events present new difficulties. Video systems which record and display races in a standard television or video format are popular, but regardless of the particular implementation of these systems, a portion of the electronic image remains on an analog medium, such as recording tape. Since analog data from the systems consists of a continuum of information over time, it is relatively difficult to accurately apportion to a unique time interval. It is even more difficult to access a particular moment in time in the recorded sequence because the associated system must search the storage medium, typically having a long physical length in a spooled format, e.g., a video cassette. This presents both limitations and difficulties for users wishing to simultaneously record, view the current race, and review earlier segments of the race (or even a previous race) because only one user can have access to any of the information stored and recorded at any one time.
A further difficulty in analog data is that it must be converted to a signal usable for video, television, or a computer before it is displayed. For example, after a completed search, a selected video tape segment is typically sent to active memory before it can be processed by a computer and, quite possibly, by supplemental complex graphics generators. Altogether, the analog format and related processing adds to the time required to review a race and therefore lengthens the decision making process.
Another problem faced by race systems occurs in the management of extended time events, like a marathon or bicycle race, which can last for hours or until each entrant finishes. The runners or cyclists cross the finish line in groups; and for long periods, the finish line is void of persons. The relevant information at the finish line is thus sporadic, and includes significant amounts of xe2x80x9cdeadxe2x80x9d time. In analog systems, this dead time is nevertheless recorded and stored so that the image record will retain time synchronism with the event, even though the intervening dead time images are generally useless for other reasons and add to the time required for processing and reviewing the race.
Several race systems have attempted to improve the management and accessibility of data taken during a race by transforming the recorded information to a digital equivalent. But, these systems also often revert to an analog format before displaying the race on a screen. As examples, U.S. Pat. No. 4,797,751 shows a video recording system having both digital and analog sections to provide display on a common cathode ray tube (CRT). U.S. Pat. No. 5,136,283 similarly describes another partially digital system which displays races on a standard television format. These analog/digital systems still have many of the problems inherent in entirely analog systems.
Linear sensor arrays or line cameras as described more fully in the above-mentioned commonly owned ""824 and ""077 patents, have now also been applied to such imaging tasks. These cameras have been used for assembly line imaging as well as for athletic competition finish line imaging. They offer the advantage of extremely accurate time resolution of a restricted area, namely of a linear strip imaged by the camera, and by taking a time series of frames directed at a fixed station, a two-dimensional linear/temporal or t,y-dimension image may be formed that bears a readily interpretable similarity to the customary optical spatial or x,y-dimension image of the scene. As set forth in applicant""s above mentioned patents, the data stream from such cameras can be used to detect and deal with moving objects to provide high temporal and spatial resolution in real time. This entails transmission of a generally continuous stream of line image data to a processing system, which then attends to the annotation, indexing, compression and storage of the relevant views so that a small sub-portion of relevant views can be placed in digital random access storage and readily recalled, typically within minutes or seconds of the original image acquisition, for detailed inspection. However, effective use of such line-imaging camera systems has required extensive software-mediated data handling by a trained technician operating the system, and great demands are imposed on the data transmission and synchronization for effecting image assembly, time synchronization, and image frame recording and access.
It is, accordingly, an object of the invention to provide an improved camera and system for recording and displaying a time-sequential scene of bodies crossing a plane along a track.
These and other objects will become apparent in the description below.
The invention features, in one aspect, a camera for forming a time sequential scene of bodies moving across a plane in space, wherein the camera recognizes the appearance of an object within its limited field to trigger or flag its image output stream. The system includes at least one camera which is aimed to image objects crossing a line of interest, wherein the camera time-sequentially captures the object by imaging it onto an array of detector elements and converts the sampled signal into a digital line image, or frame, which passes to a frame buffer. Each digital image frame uniquely represents a fixed slice of the moving scene at a moment in time. A processor is situated within the camera, and communicates with the buffer, processing information from corresponding pixels or larger blocks of time offset frames to detect an object which has entered the line field of view and responsive thereto, controls the image data output stream or produces data coordinated with the image stream. For example, in one aspect, the camera detects arrival or departure of objects in the image field and thereupon operates to produce or enable an image data output stream, or to annotate the stream and enhance its information content by indicating such detection. In a basic aspect, the camera may detect entry or departure of a probable object at the image field, and tag or enable the relevant portion of the image stream. In a further aspect, the camera operates on the detected image data to make object-based determinations. In this aspect of the invention, the processor inspects image features, such as shape or orientation of the presenting features, or duration of the features, and confirms the presence of an object. It may then make a further determination, such as the identity of the object, or the probable crossing time of the object, to provide an output data stream which annotates information or results, greatly facilitating the processing of event data and the real time announcement of results.
In a basic embodiment, the processor detects the start of one or more objects crossing a finish line, and enables the image data output stream from the camera only during the interval when activity appears in that region. Static or background image frames may be flagged for separate or non-critical handling, may be sent to a separate port which interfaces with a data local storage unit, or may be simply suppressed and later be reconstructed from earlier or later frames. Thus, in one embodiment, frames of a displayed scene which add no information are removed, either temporarily or permanently, effectively withholding from the stream those frames in which there are no activity or bodies crossing the planexe2x80x94while retaining a time reference for the remaining frames, which collectively display all the visible changes of a continuous scene. Alternatively, rather than suppressing the static portions of the image stream or acting as an on/off control of the output stream, the processor may simply flag the active (or the static) frames of the stream so that an external processor receiving the camera output is able to operate more effectively to code, index and store the relevant image frames in suitable memory locations for access, inspection, or other processing or reconstruction as appropriate.
In a further embodiment, the processor processes frame data when frame changes have indicated the presence of a contestant at the imaged field, to perform a photocell determination. This processing sorts or compares blocks of frame data corresponding to features, such as the head or body of a horse, or the arms, legs and torso of a runner, to confirm the presence and position of a finish line crossing. The processor then determines, typically by interpolation or back-interpolation, the line-crossing time, which may for example be associated with the nose of the horse, or torso of the runner. These determinations are typically made by software feature checking routines which scale the body size of the object to the expected velocity of the event and the frame rate of the camera to estimate the exact finish line time. By detecting body features in the correct order before triggering the finish line time determination, or by otherwise confirming the presence of an object, the camera avoids falsely triggering, for example on a shadow of a back-lit runner that may precede the actual crossing.
In yet another or further embodiment, the processor processes frame data to detect patterns or markings on the imaged objects, such as numbers identifying the contestants, and the output frames in which these objects or indicia were detected are flagged or indexed with the detected identifiers. The line camera may be set up at a plane of interest, such as the finish line of a race or an intermediate position along the track. In this case, the frame times may also be processed with the flagged identifiers at the observed plane, either the finish line or an intermediate position, to quickly show rankings or relative positions, speed or other ratings for immediate display in an automated manner without waiting for a judge""s inspection of the digitally reconstructed images as required in previous image timing systems. The camera output augmented with this data thus directly interfaces with a computerized race management system so that desired frames are quickly accessed by their index information for review. A user at the computer console can command a variety of functions provided by the invention to manipulate and analyze the captured scene, most particularly to display any portion of the scene of bodies moving across the plane and access an associated time and/or identities of contestants for each frame within the sequence of line crossing images.
The system of the invention is particularly useful in recording and managing the official times of objects or entrants crossing a finish line in a digital race management system since it both preserves all imaging information and simplifies the storage, transmission and selective retrieval of finish line information. A user can therefore record and display the bodies crossing the plane of interest, i.e., the finish line, with accuracy while enhancing the ability to immediately employ information embedded in the images in real time, both to review and edit the stored images for finish determinations, and to effect fast automated display of unreviewed results. The invention thus provides an object-controlled compression and information enhancement of the camera output data.
The system constructed in accordance with the invention also provides, in another aspect, an in-camera memory subsystem communicating with an in-camera processor, wherein blocks of frame data are processed to detect an object, to detect a background, and to control start time and/or end time for active imaging segments which are to be transmitted out of the camera for analysis. According to this aspect of the invention, the processor may analyze imaged frames and set a retroactive start time for frame transmission, or a prospective end time to assure integrity of the preserved image record. A timer in the camera maintains a common time line, and the frames in transmitted segments are time labeled. In addition to finish line and mid-course tracking and identification, the camera and system are also useful for various photocell determinations.